title: Hypoxia regulates the sperm associated antigen 4 (SPAG4) via HIF, which is expressed in renal clear cell carcinoma and promotes migration and invasion in vitro.
abstract: Hypoxia leads to the upregulation of a variety of genes mediated largely via the hypoxia inducible transcription factor (HIF). Prominent HIF-regulated target genes such as the vascular endothelial growth factor (VEGF), the glucose transporter 1 (Glut-1), or erythropoietin (EPO) help to assure survival of cells and organisms in a low oxygenated environment. Here, we are the first to report the hypoxic regulation of the sperm associated antigen 4 (SPAG4). SPAG4 is a member of the cancer testis (CT) gene family and to date little is known about its physiological function or its involvement in tumor biology. A number of CT family candidate genes are therefore currently being investigated as potential cancer markers, due to their predominant testicular expression pattern. We analyzed RNA and protein expression by RNAse protection assay, immunofluorescent as well as immunohistological stainings. To evaluate the influence of SPAG4 on migration and invasion capabilities, siRNA knockdown as well as transient overexpression was performed prior to scratch or invasion assay analysis. The hypoxic regulation of SPAG4 is clearly mediated in a HIF-1 and VHL dependent manner. We furthermore show upregulation of SPAG4 expression in human renal clear cell carcinoma (RCC) and co-localization within the nucleolus in physiological human testis tissue. SPAG4 knockdown reduces the invasion capability of RCC cells in vitro and overexpression leads to enhancement of tumor cell migration. Together, SPAG4 could possibly play a role in the invasion capability and growth of renal tumors and could represent an interesting target for clinical intervention.
authors.affiliation: Department of Nephrology and Hypertension, University of Erlangen-Nuremberg, Erlangen, Germany; Nikolaus Fiebiger Center, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Karl Xaver
authors.initials: KX
authors.lastname: Knaup
authors.forename: Juliana
authors.initials: J
authors.lastname: Monti
authors.forename: Thomas
authors.initials: T
authors.lastname: Hackenbeck
authors.forename: Tilmann
authors.initials: T
authors.lastname: Jobst-Schwan
authors.forename: Bernd
authors.initials: B
authors.lastname: Klanke
authors.forename: Ruth Elisabeth
authors.initials: RE
authors.lastname: Schietke
authors.forename: Ingrid
authors.initials: I
authors.lastname: Wacker
authors.forename: Juergen
authors.initials: J
authors.lastname: Behrens
authors.forename: Kerstin
authors.initials: K
authors.lastname: Amann
authors.forename: Kai-Uwe
authors.initials: KU
authors.lastname: Eckardt
authors.forename: Christina
authors.initials: C
authors.lastname: Warnecke
authors.forename: Michael Sean
authors.initials: MS
authors.lastname: Wiesener
mesh_terms: D002292:Carcinoma, Renal Cell / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D000860:Hypoxia / Q000235:genetics*; D051793:Hypoxia-Inducible Factor 1 / Q000235:genetics*; D007680:Kidney Neoplasms / Q000235:genetics*; D009361:Neoplasm Invasiveness / Q000235:genetics*; D015854:Up-Regulation / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D051793:Hypoxia-Inducible Factor 1; C114799:SPAG4 protein, human
keywords: cancer; transcription factor; translation; tumor